Metal film based micro- and nano- cavities: optical polarization and wavevector studies

Abstract

Probing light-matter interaction is at the heart of nanophotonics. Studying the interaction of light with molecular emitters have wide implications including applications like developing molecular probes for sensing, molecular antennas etc. To achieve control over the molecular emission and harness it, one has to modulate emission parameters like intensity, wavevectors, and polarization of the molecular emitter. In this context, various cavity architectures have been studied to manipulate molecular emission. Design of cavity architectures play a very critical role in tailoring the emission properties from the cavity. Architectures based on metallic nanostructures, dielectric resonators, hybrid metal-dielectric cavities can be used to tailor specific parameters of light-matter interaction effectively. Metal film based cavities have emerged as an important design architecture in the recent times. This design facilitates flexibility to create both metal and metal-hybrid based cavities. In the past, intensity enhancement of molecular emission in cavities has been studied extensively. But the effect of cavity on wavevector distribution and polarization of molecular emission signatures have not been studied in great detail. Understanding them, potentially, can give rich information about the coupling strength of the interaction, modes of the cavity and much more. It can also be used to efficiently design cavities focusing on antenna aspect of the cavity design. Herein, we discuss the effect of different metal film based cavities on the wavevector and polarization states of the molecular emission coupled to them. We probe various metal-dielectric hybrid cavities using Fourier plane imaging and spectroscopy. First, we discuss the effect of an elongated cavity created using plasmonic nanowire placed on gold film on the wavevector signatures of molecules sandwiched between the wire and the film. We discuss the effect of such extremely small cavities on different relaxation process like Raman scattering and molecular fluorescence. Next we present the effect of vertical molecular nanowire cavity coupled to thin plasmonic film on its emission pattern as a function of operational wavelength. Finally, we will discuss the effect of microsphere cavity placed on metal film on wavevector and polarization states of molecular emission.